The invention relates to a hydraulic damping two-chamber engine mount including a working chamber and a compensating chamber filled with a hydraulic fluid and separated by an intermediate plate in which an overflow passage, at least one switchable bypass passage and an isolating diaphragm are disposed.
In such hydro-mounts the static load is handled by a supporting spring surrounding the working chamber. The hydraulic damping is affected by a column of fluid oscillating in the overflow passage. The task of the isolating diaphragm in hydro-mounts is to hydraulically isolate low-amplitude vibrations introduced into the system, i.e. to prevent the overflow passage from becoming active, thus eliminating all damping effects. As a result, the mount has an ideal soft response to small amplitudes. It is not until the isolating diaphragm is more or less totally deformed and/or at a stop that fluid also flows through the overflow passage and thus produces a hydraulic damping as well as enhanced stiffness. The isolating diaphragm is required to isolate small amplitudes, especially noise-relevant amplitudes, over as large a frequency range as possible.
The bypass passage is opened in critical operating situations to permit adapting the mount thereto. Opening the bypass passage achieves a reduction in the dynamic stiffness below the static stiffness, which is termed underswing or undershoot. An underswing or undershoot is particularly advantageous when the engine is idling because the mount is then able to better isolate the vibrations occurring particularly during engine idling.
When the isolating diaphragm and the bypass passage are incorporated together in a mount, they need to be tuned to each other. However, it is that tuning which results in an unsatisfactory overall result. The reason for that is that the amplitude of the vibrations upon idling is only slightly larger than that of the noise-relevant vibrations. Optimal tuning with the bypass passage opened results in a poorer response when the bypass passage is closed, i.e. with noise or an unsatisfactory functioning being the result.
It is accordingly an object of the invention to provide a hydraulic damping two-chamber engine mount, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and in which a bypass passage can be simply switched.
With the foregoing and other objects in view there is provided, in accordance with the invention, a hydraulic damping two-chamber engine mount, especially for a vehicle, comprising a working chamber and a compensating chamber to be filled with a hydraulic fluid; an intermediate plate separating the chambers from one another; an overflow passage disposed in the intermediate plate; at least one switchable bypass passage disposed in the intermediate plate; an isolating diaphragm disposed in the intermediate plate; and an actuator associated with the isolating diaphragm for rotating the isolating diaphragm into a first rotatable position closing the bypass passage and a second rotatable position opening the bypass passage.
With the bypass passage opened, damping and isolating is achieved practically exclusively by the bypass passage. The concept for this operating condition can be made independently of the isolating diaphragm so that the isolating diaphragm can be optimally constructed for operation with the bypass passage closed, thus permitting better adaptation to both conditions of the mount. Switching the bypass passage is achieved with a simple configuration by using the rotatable isolating diaphragm.
In accordance with another feature of the invention, there is provided a device associated with the isolating diaphragm which fixes the isolating diaphragm axially in the second rotatable position and causes the isolating diaphragm to be blocked when the bypass passage is opened so that it makes no further contribution.
In accordance with a further feature of the invention, the actuator for rotating the diaphragm may be disposed in the compensating chamber or in the working chamber. The actuator may be secured directly to the intermediate plate or to a separate mounting part. The actuator is advantageously configured as an electric motor or as a solenoid actuator.
In accordance with an added feature of the invention, the isolating diaphragm is disposed non-rotatably on a shaft of the actuator but is axially shiftable. The isolating diaphragm may be configured to be round, oval or star-shaped and flexible or rigid.
In accordance with an additional feature of the invention, depending on the configuration, the isolating diaphragm may open the bypass passage through one or more ports, the number of which advantageously corresponds to the number of the bypass passages. Upon rotation, the ports coincide with at least one of the bypass passages to thus open it. Closing it occurs by the repeat rotation of the isolating diaphragm in the opposite direction or further in the same direction.
When a round diaphragm is used, these ports are a mandatory requirement. Where an oval or star-shaped diaphragm is concerned, the locations having a larger diameter serve to close the at least one bypass passage.
In accordance with yet another feature of the invention, in order to axially fix the isolating diaphragm in place, protuberances are provided on the isolating diaphragm which cooperate with constrictions in the intermediate plate. The height of the constrictions is less than the overall height of the isolating diaphragm and the protuberances. When the isolating diaphragm is rotated, the protuberances coincide with the constrictions and fix the isolating diaphragm in place. Any movement in the direction of the longitudinal center line of the isolating diaphragm or flexing is reliably prevented in order to thus eliminate the damping action of the isolating diaphragm when the bypass passage is opened.
In accordance with a concomitant feature of the invention, the protuberances may vary in shape and may, for example, be round, half-round or bead-shaped and may be disposed on one or both sides of the isolating diaphragm.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a hydraulic damping two-chamber engine mount, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.